CVE-2026-6850
Published:July 13, 2026
Updated:August 04, 2026
Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to validate the length and content of message attachment field values, which allows an authenticated attacker to cause a denial of service for all users in a channel via a post containing a specially crafted payload that triggers catastrophic backtracking in the client-side markdown parser.. Mattermost Advisory ID: MMSA-2026-00658
Affected Packages
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.7.0 <v11.7.3Fix Suggestion:
Update to version v11.7.3github.com/mattermost/mattermost (GO):
Affected version(s) >=v10.11.0 <v10.11.20Fix Suggestion:
Update to version v10.11.20github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.6.0 <v11.6.5Fix Suggestion:
Update to version v11.6.5Related Resources (3)
Do you need more information?
Contact UsCVSS v4
Base Score:
7.1
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
LOW
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
NONE
Vulnerable System Availability
HIGH
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
6.5
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Weakness Type (CWE)
Inefficient Regular Expression Complexity
EPSS
Base Score:
0.24